On Wed, 4 Sep 2002, Dennis Ritchie wrote:- The picture of Dennis and Ken in front ASR-33's hints at a pdp11/20 logo on the console. The 11/20 I have (built 29/1/71, SN 821) has just plain 'pdp11'. The lead time on getting the machine was about 6 months. I suspect that the /20 was added as other models were in the pipeline (/05,/45). For a picture, see http://www.psych.usyd.edu.au/pdp-11/11_20.html Indead it was The front cover is interesting, in that it shows a table top version of the 11/20. It was quite possible to run one just with paper tape and an ASR33 with the reader/punch option. There was a similar option for the pdp8/e. The only obvious change between the first and second edition handbooks was that the latter changed the last page from a picture of a young lady in front of a machine to a table of Unibus pin assignments.